Guidelines for Grounding and Earthing for Systems between Buildings

Problems that arise with systems that encompass more than one building

A system is not always accommodated within one building, but can stretch across two or more buildings. This means there are power and/or signal cables going from one building to another.

If both buildings have independent ground connections and grounding systems, it can lead to an interfering potential difference between the end points of a line running between buildings.

In the event of a lightning strike on one of the buildings this potential difference can become so high that destructive transient currents can be sent down the line. People and animals can also be endangered if parts of the buildings can be touched simultaneously.

Guidelines for grounding and earthing between buildings

When a system is installed across more than one building the following guidelines for grounding and earthing must be observed:

Earthed parts that can be touched simultaneously must be connected to the same earth connection.
A suitable potential compensation lead must be installed between the buildings grounding systems that is capable of dissipating transient currents caused by lightning strikes.

NOTE: All lines going in and out of the system to be protected must be connected to the earthing system directly via spark gaps or protective devices (lightning arrestors). In the event of a lightning strike the potential of the system struck increases temporarily but no dangerous potential difference occurs within the system.